Vibration damping of ultra-light belt conveyor galleries

The Swiss companies MartiTechnik AG and K.Bitterli+Partner Ingenieure AG have cooperated with the Swiss Federal Laboratories for Materials Science and Technology (EMPA - Eidgenössische Materialprüfungs- und Forschungsanstalt) in a research project to reduce vibration in ultra-light belt conveyor galleries since April 1, 2013. The project is financed by the two companies mentioned above and the Federal Commission for Technology and Innovation (Kommission für Technologie und Innovation (KTI project 14871.1 PFIW-IW) des Bundes).

The aim is to develop a bridge as light as possible with a span of 50 m as the supporting structure for belt conveyors. The bridge's lightweight and simple design offers huge advantages for construction as well as transport and assembly. The bridge's standard components are to be produced centrally with the highest possible degree of automation for worldwide shipment in containers to the place where the bridge is used.

The goal: reducing vibration

In general, lightweight bridges with wide spans are prone to vibration. This means that the external stimulus of forces such as wind, machines or persons induces vibration. The KTI project's aim is to find a way to dampen vibration in lightweight steel bridges. The damping needs to be adapted to variable influences arising from variations in the bridge weight resulting from the flow of material on the conveyor belt. This requires active damping. The damping system automatically adapts to varying conditions.

From the model to full implementation

A 1:20 scale model of the new bridge type was built and fitted with type KMR force washers in May 2013. This model was used to carry through different tests regarding assembly and operation. Since in this case the measurements were only taken to verify the FEM results, cost-effective miniature force washers could be used.

The original-size bridge was installed in a gravel plant in late July 2013. It is made of steel and stabilized by four pre-stressed wire ropes. C6A force transducers from HBM each with 1000 kN measuring range  were installed in all of the four ropes for monitoring of the pre-stressing force during assembly and operation. Type AE301 industrial amplifiers were used for evaluation. Jakob Baader, Senior Project Engineer at Bitterli+Partner Ingenieure AG says: "HBM offers a very attractive price-performance ratio and products that can also be used in harsh environments." The measurements were highly reliable and stable. A vibration damper optimally adapted to the bridge will now be developed based on the acquired measurement data.

"HBM offers a very attractive price-performance ratio and products that can also be used in harsh environments."

Jakob Baader
Senior Project Engineer
Bitterli+Partner Ingenieure AG

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